Shogaols have been known to have antipyretic action, analgesic action, anti-inflammatory action, antioxidant action and an action to suppress biosynthesis of prostaglandin in addition that shogaols are used as food flavor. Shogaols are very important compounds industrially (for example, “Development of Pharmaceutical Products”, Vol. 2, Pharmacologically Active Substances II, 1988 edition, Hirokawa Shoten). However, shogaols exist only at a trace amount in naturally occurring materials. Additionally, the isolation and purification of shogaols from naturally occurring materials requires laborious works. Thus, the development of an industrial method for producing shogaols via chemical reactions has been desired.
As a process for producing shogaols, a method is known, which includes a step of reacting gingeron and an aliphatic aldehyde together in the presence of a base to prepare gingerols and further heating the resulting gingerols in the presence of an acid catalyst for dehydration to modify the gingerols into shogaols (Official Gazette of JP-A-8-40970). However, the method described in the Official Gazette was problematic in that the yield of gingerols was so low despite the use of an excess amount of the aliphatic aldehyde that shogaols could not be obtained at a good yield.
It is an object of the invention to provide a process for producing shogaols, by which shogaols can be produced at a high yield.